Asteroids on a collision course with Earth - should we worry

ALLEN MARQUETTE

May 15, 2008 at 4:26PM AKST

Everyone’s seen science fiction B movies where aliens are trying to invade the Earth and destroy life as we know it.

So far that we know, no aliens have visited the Earth yet, but there is concern by scientists of the possibility of a visitor from space in the form of an asteroid affecting life on Earth.

While many astronomers are kept busy with deep space research by studying nebulas, galaxies and other interesting anomalies in the greater voids of space, other scientists are looking for asteroids and other large chunks of material left over from the formation of our solar system and beyond.

Government agencies and private individuals are diligently searching the nighttime skies with little funding to try to locate these rogue space missiles before they arrive on our doorstep unannounced.

In the past millions of years, Earth has had many near misses, but most everyone has heard of the one that didn’t miss Earth 65 million years ago. It ended the reign of the dinosaurs and set the stage for mammals to step up to the plate.

In the past 600 million years, there have been five major mass extinctions that on average extinguished half of all species on Earth. The largest mass extinction to have affected life was in the Permian-Triassic, which ended the Permian period 250 million years ago and killed off 90 percent of all species living on Earth.

These large devastating impacts don’t happen very often on Earth, but it would be nice to know if any asteroids are headed our way in the near future.

When a large enough chunk of space rock is detected as a potential threat to Earth because of its size, careful mathematical measurements and calculations are worked out for its trajectory and the possibility of it’s impacting the Earth sometime in the future.

So, you may ask, are there any asteroids out there with a flight plan to visit Earth sometime in the near future? Actually, there is one rock that has caused some concern among scientists called 99942 Apophis.

This asteroid is about three football fields in size and weighs in excess of several hundred thousand tons. The fact that it’s traveling at nearly 100,000 miles per hour, combined with its size, makes it pretty clear that the Earth’s atmosphere would have virtually no effect on slowing this rogue missile down before impacting the Earth.

Believe it or not, on Friday the 13th, in 2029, 99942 Apophis is scheduled to come within one-tenth of the distance the Earth is from the Moon. Some might say the date alone seems like somewhat of a bad omen.

When it does arrive, the asteroid will be close enough to be easily visible to the naked eye as it hurtles past the Earth on is course through our solar system. Even though this distance seems close, scientists estimate there is only a one in 45,000 chance of it hitting Earth.

That’s not the problem though. Apparently, asteroid 99942 Apophis is approaching so close to the Earth in 2029 that our gravitational pull will change its trajectory slightly as it rockets past Earth at 20 to 40 miles per second.

Once the asteroid’s trajectory changes, we have a whole new situation to deal with. Scientists can’t predict how much the Earth’s gravitational pull will affect the asteroid’s trajectory, but they do know its course will be altered.

Once scientists figure out its trajectory, they will have about seven years to figure out if Earth will be a target during its next pass-by in 2036.

So, if an asteroid the size of 99942 Apophois did hit the Earth, would it have the same devastating effect the last asteroid had when it impacted Earth 65 million years ago?
Probably not, since the asteroid that smashed into the Yucatan Peninsula close to the current Mexican town of Chicxulub was around six miles in diameter, scientists estimate.

In comparison, asteroid 99942 Apophis is a mere 900 feet across but still weighs in excess of hundreds of thousands of tons; the crater that this mountain of rock would carve out if it collided with Earth would destroy an area the size of Texas.

Since the Earth’s surface is more water than land, there’s a good chance the asteroid would impact in the ocean. If this type of impact occurred, tsunamis would wreak havoc on thousands of miles of coastline. Either way, the consequences would be severe.

Allen Marquette is the education coordinator for the Prince William Sound Science Center.